Henderson has returned from an excellent season on loan at Sheffield United at a time when De Gea’s position looks vulnerable after a succession of high-profile errors.
It leaves manager Ole Gunnar Solskjaer with a dilemma ahead of the new season but Neville doesn’t believe the competition is a positive thing.
David de Gea’s status as Manchester United’s No 1 goalkeeper is under increasing pressure
Dean Henderson has returned from his loan spell to challenge De Gea for the No 1 spot
The goalkeeper situation leaves manager Ole Gunnar Solskjaer facing a headache
The Old Trafford legend told Sky Sports: ‘The idea that Dean Henderson would come into Manchester United and replace David de Gea as No 1 goalkeeper straight away… it won’t happen, I can guarantee it won’t happen.
‘This has got ‘problem’ written all over it. The one area of the pitch where you need consistency and stability is your goalkeeper.
‘You need to know who your No 1 is, you cannot be flip-flopping. It just does not work; I’ve never seen it work at any club or at international level.
‘Where there is a decision to be made about two goalkeepers you have to pick your No 1, go with him and stick with him, even if there is a mistake.
‘Once you take David de Gea out of the team and put Henderson in, you may as well forget about De Gea. That’s coming from my experiences at United.
Gary Neville fears the goalkeeping situation spells trouble for Solskjaer and Man United
He expects Ole Gunnar Solskjaer (R) to keep faith in De Gea despite some high-profile errors
De Gea makes a mistake in Man United’s defeat to Watford back in December last year
‘The period between Peter Schmeichel and Edwin van der Sar we had Ricardo, Fabien Barthez, Mark Bosnich, Roy Carroll, Tim Howard, Massimo Taibi, many goalkeepers over a five to six-year period and there was inconsistency that certainly didn’t help.’
Spain international De Gea, 29, has been United’s No 1 goalkeeper for nine seasons now and is regarded as one of the game’s best shot-stoppers.
But mistakes have crept into his game with Watford, Tottenham Hotspur and Chelsea among the opponents to benefit last season.
The 23-year-old was impressive for Sheffield United and has no plans to be second choice
Henderson impressed for Sheffield United on their Premier League return and the 23-year-old, who has been on United’s books since 2011, has made it clear he doesn’t want to serve as De Gea’s back up.
United get their Premier League season underway at home to Crystal Palace on Saturday after being given an extra week of pre-season following their run to the Europa League semi-finals.